Feeling the heat

Jack Board

BANGKOK (CNA) – Prasert Saisamphan’s home used to be a breezy space, surrounded by trees. Now, the 65-year-old finds it hard to breathe, surrounded by confining concrete and the dust of a growing city.

“When I was about 20 years old, condominiums were not built here yet. The weather was nice and cool. We only used a fan in the evening. No one had an air-conditioner in my house,” he said. “Now, there’s less air. It feels like I can’t take a deep breath.”

The view from Prasert’s house in Klong Khlang in central Bangkok is dominated by the towering pylons of an expressway, and in the distance, seemingly ever-growing residential towers.

“It’s hot this year. It’s so hot that the electricity charges significantly rise. It’s so hot that I installed water sprinklers on the roof. It’s so hot that I need water spray. It feels doubly hot compared to last year,” said Jurairat Kruephimai, another local resident.

The heat they feel is not imagined. The effect of a phenomenon known as the urban heat island (UHI) is in force in Bangkok, causing the maximum temperatures to rise higher than the surrounding areas. It is particularly felt at night.

Night time is meant to provide the body with a chance to cool but heat is trapped by thermal mass during the day and released at night. PHOTOS: CNA

Green space has dramatically been lost in large Asian cities as urban expansion grows
Prasert Saisamphan relies on shade from a tree near his home to stay cool

Roads, buildings and other concrete urban infrastructure absorb solar radiation during the day and release it slowly at night, causing an increase in temperature. Vehicles add to the issue as well as the clearing of green spaces to make way for new construction.

Dr Sigit Dwiananto Arifwidodo from Kasetsart University has extensively studied UHI in the Thai capital. In 2012, one of his studies found that the maximum temperature difference between urban and rural areas was seven degrees Celsius. And up to 2018, he noted that temperatures amplified by UHI continued to increase year on year.

“Higher temperatures because of the urban heat island effect are rising every year. At first, we were surprised,” Dr Arifwidodo told CNA. “When we map it out, the area that is a hotspot is getting bigger and bigger. The latest one where we used the data from 2018, it’s almost the whole of Bangkok.”

Bangkok is not alone in having to contend with the UHI problem – it is increasing in regularity and magnitude across Asian cities, as urban areas expand, green areas decrease and poor air ventilation stifles dense spaces.

While hot temperatures in the day pose risks for workers exposed to prolonged periods outdoors, research shows that it is at night when more damage can be done, in the form of heat stroke or exhaustion.

A recent study by the Chinese University of Hong Kong (CUHK) highlighted the dangers of consecutive nights of increased temperatures as a result of climate change and the urban heat island effect.

In July, Hong Kong experienced a heat wave that brought a “very hot warning” for 20 consecutive days. The hot night-time temperatures were found to significantly intensify health impacts.

“Nighttime is supposed to provide the body with a chance to recover and rest from the heat of the day, but ‘hot nights’ make the recovery and resting less effective,” said Dr Kevin Lau, a research assistant professor from the Institute of Future Cities at CUHK.